Add admin_menu_permission hook to menu.php

[donncha]

WordPress MU has a modified wp-admin/menu.php but with the addition of a new hook just above the user_can_access_admin_page() check, those custom mods can go into a new file.

I called the action admin_menu_permission as there are hooks above for modifying the admin menu, this hook wouldn't have any other function AFAICT.

I did try hooking on to admin_menu but it didn't work and the user received the standard WP "cannot access page" error instead of being redirected as WordPress MU usually does.

Please take a look at the attached file.

Looking at the mu code ( http://trac.mu.wordpress.org/browser/trunk/wp-admin/menu.php) would we not do better with an action inside the failure case:

e.g.

if (! user_can_access_admin_page()) { 
    do_action('admin_page_access_denied');
    wp_die( __('You do not have sufficient permissions to access this page.') ); 
} 

mu can then hook on that and do the redirect if necessary before the wp_die

This could also then be used by any WordPress plugins that wanted to track things like attempts to access pages that the user didn't have the rights to.

Good idea, looks better inside the if() condition.

(In [6356]) Allow plugins to handle admin page access failures. Fixes #5379 props donncha